Method of manufacturing fluid heat exchange apparatus



y 1956 E. E. SCHOESSOW METHOD OF MANUFACTURING FLUID HEAT EXCHANGEAPPARATUS Filed Aug. 15, 1952 NVENTOR far! I cSZZZ06SS07M ATTORNEYUnited States Patent METHOD OF MANUFACTURING FLUID HEAT EXCHANGEAPPARATUS Earl Edward Schoessow, Barber ton, Ohio, assignor to TheBabcock & Wilcox Company, New York, N. Y., a corporation of New JerseyApplication August 15, 1952, Serial No. 304,574

2 Claims. (Cl. 29-157.

The improvement of this invention relates to fluid heat exchangeapparatus operable at substantial fluid pressures. The inventioninvolves a method adapted for the manufacture of such apparatus, and themethod is particularly concerned with the securement of tubes to thepressure parts of the apparatus in such a manner as to provide pressuretight connections without undesirably stressing the main parts of thetubes.

Specifically, the invention involves the swaging down of parts of thetubes to form, for each tube, one tube seat portion of a diameter lessthan the diameter of the remainder of the tube, the formation of tubeseats in the pressure parts to slidably receive the swaged down tubeseat portions and other tube seat portions of larger diameter, thefitting of the tube seat portions in their proper tube seats in thepressure parts, the expanding of a larger diametered portion of a tubeinto its tube seat, and then the expanding of the swaged down tube seatportion of the same tube into its fitting tube seat by expanding actionwhich does not involve tube metal flow toward the previously expandedtube seat portion of the same tube. This method permits the use of aball drift expander of one diameter for the larger diametered tube seatportion, the passage through the unswaged parts of the tube of a smallerdiametered ball drift expander for expanding of the swaged down tubeseat portion by movement in the same direction (longitudinally of thetube) as the move ment of the first expanding operation. This procedurepermits tube metal flow in the same direction for both expandingoperations effected in each tube, and thereby prevents undesirable tubestressing which might result in the bowing of the main parts of thetubes or the impressing of forces tending to disturb the operativepositions of the pressure parts (or tube sheets).

The illustrative method is particularly advantageous, in the manufactureof the pertinent type of heat exchange apparatus by incrementalexpanders which eifect tube metal flow in one direction away from thestarting point of the expanding operation, and the type of expanderinvolved may be other than a ball drift expander.

The method of the invention is particularly and concisely set forth inthe subjoined claims, but, for a better understanding of the invention,its uses and advantages, recourse should be had to the followingdescription which refers to similarly characterized parts in theaccompanying drawings.

In the drawings:

Fig. 1 shows a heat exchange tube to be secured in pressure tightrelationship to spaced pressure parts having tube seats therein;

Fig. 2 is an elevation of a tube with its ends shown in section toillustrate the step of swaging down one end of the tube to form a tubeseat portion of a diameter less than the diameter of the remainder ofthe tube;

Fig. 3 is a section (with a part of the tube in elevation) illustratingthe step of fitting the tube into tube seats in opposed tube sheets ofpressure parts, with the swaged down tube seat portion fitted into atube seat of a diam- "ice eter less than the diameter of the tube seatreceiving the other end of the tube;

Fig. 4 is a view similar to Fig. 3, but showing the final part of theaction of a ball drift expander in expanding the larger diametered tubeseat portion into its fitting tube seat; and

Fig. 5 is a view similar to Fig. 3, but showing a ball drift expanderabout to become effective on the swaged down tube seat portion, afterhaving been passed through the unswaged portions of the tube.

Starting with a tube 10, of uniform diameter, the practice of theinvention involves the swaging down of the right hand end of the tube toform the smaller diameter tube seat position 12. The tube is thenoperatively disposed relative to the walls 14 and 16 of pressure parts(such as drums, headers, or the tube sheet walls of the other pressurechambers). The wall 14 has previously been drilled to form the tube seat18 to slidably fit the left hand end of the tube, and the wall 16 hasbeen drilled to form the smaller diameter tube seat 20 to slidablyreceive the swaged down tube seat portion 12.

Next, a ball drift expander is utilized to expand the larger diameteredtube seat portion 13 into the tube seat 18. This expander is shown ashaving a stem 24, unitary with a head or ball 26 of such a diameter,slightly larger than the inside diameter of the tube, that as theexpander is forced in the direction of the arrow 28, into the tube, theleft hand end of the tube (or its larger diametered tube seat portion)is expanded tightly into the tube seat 18. This action, to secure thedesired pressure tightness, stresses the metal of the tube seat, whilecausing tube metal flow in the direction of advance of the expander.

Fig. 4 shows the expander 22 at the end of its effective expandingoperation, at a position close to the plane of the right hand surface ofthe wall 14. When the expander has reached this position it is withdrawnfrom the tube, and another similar expander 30 is passed into and alongthe tube from the dotted line position 32 of Fig. 5 to the full lineposition indicated near the opposite end of the tube. This expander hasa head or ball 34 of such a diameter, slightly larger than the insidediameter of the swaged down tube seat portion 12, that its passagethrough that tube seat portion 12 in the direction of the arrow 40 willexert enough expansive force to stress the tube seat 20, while causingmetal flow in the same direction as the metal flow of the expandingoperation at the other end of the tube.

When the tube seat walls 14 and 16 are formed by fixed tube sheets, orfixed headers, a large number of parallel and closely spaced tubes maybe secured in pressure tight juncture with those pressure parts withoutplacing the tubes under such compressive stresses as might otherwise becreated. For example, if both ends of each tube were protractivelyexpanded (that is, by action advancing from a tube end toward a pointmidway of the length of the tube) the main part of the tube would beplaced under substantial compressive stresses, and if the magnitude ofthese stresses were great enough the tubes might be bent so as tointerfere with their proper operative spacing, or the connected pressureparts might be placed under undesirable stresses. In this connection itis to be noted that the illustrative method involves protractiveexpanding at the left hand end of the tube, and retractive expanding atthe opposite end of the tube. Also, both expanding operations are of theincremental type, with the effective force of the expanding operationactive, at any one instant, over a very small increment of the totalsurface of the tube seat, or the total surface of the tube seat portionto be expanded.

While in accordance with the provisions of the statutes I haveillustrated and described herein the best form and mode of operation ofthe invention now known to me,

those skilled in the art will understand that changes may be made in theform of the apparatus disclosed Without departing from the spirit of theinvention covered by my claims, and that certain features of myinvention may sometimes be used to advantage without a corresponding useof other features.

What is claimed is:

1. In a method of securing tubes in pressure tight relationship tospaced pressure parts to be connected by the tubes, swaging down one endonly of each tube to form a tube seat portion of a diameter than theremainder of the tube, positioning the opposite ends of each tube intofitting tube seats in the pressure parts, protractively expanding thelarger diamet'ered end of an individual tube into its tube seat, passinginto the tube from its expanded end a solid head expander of largerdiameter than the inside diameter of the swaged' down tube seat portion,and therewith retractively incrementally expanding the swaged down tubeseat portion of that tube into its tube seat, and repeating the abovespecified sequence of operations for each of the remaining tubes.

2. In the manufacture of a fiuid heat exchange unit having amultiplicity of small diameter tubes connecting pressure parts having apair of tube seats of diiferent diameters therein for individual tubes,reducing the diameter of one portion of each tube near one end thereof,fittin the tubes into their corresponding tube seats and in connectingrelationship to the pressure parts, fixing the unreduced portion of atube in its fitting tube seat and in pressure tight relation toits.associated pressure part, retractively and incrementally ball driftexpanding a reduced portion into its fitting tube seat by solid balldrift action initiated through the fixed portion and proceeding throughthe reduced end portion and out of the tube at the adjacent tube end,and repeating the above specified operation for succeeding tubes.

References Cited in the file of this patent UNITED STATES PATENTS1,647,447 Hartnett Nov. 1, 1927 1,964,051 Gordon June 26, 1934 2,275,451Maxwell Mar. 10, 1942

